Johnny Sexton is in a race to be fit for the Six Nations after his injury-hit season took another turn for the worse last night.
The Ireland out-half was forced off after 22 minutes of the 24-24 draw against Castres with a calf injury, although Leinster boss Leo Cullen was cautiously optimistic that he wouldn't be ruled out of the opening game against Scotland in two weeks' time.
The draw means only a bonus-point win by 62-plus points for Connacht in Toulouse tomorrow can deny the three-time champions a home quarter-final as they eked out a draw despite losing Sexton and captain Isa Nacewa to injury.
The Leinster No 10 has endured a wretched period since missing last year's summer tour with shoulder surgery and this latest soft-tissue injury will cause him huge frustration.
"He just had a bit of stiffness in his calf," Cullen said. "We'll see how he presents (next week). It's very early days yet (to determine if he's a Six Nations doubt). I don't imagine so but I don't know, we'll wait and see.
"He'll get scanned and he has all next week and the week after before he gets into that first game."
The injury throws further attention on the duel between Ulster's Paddy Jackson and Bordeaux's Ian Madigan who go head to head at Ravenhill today with Jackson now the favourite to wear the No 10 jersey at Murrayfield.
Sexton, 31, has been plagued with hamstring problems this season after suffering an initial tear on his left leg in the build-up to the first meeting with Castres. He missed that game. He has not finished a match since.
He came off at half-time against Montpellier and he got through an hour in the win over New Zealand at Soldier Field in Chicago.
Two weeks later, he tore his right hamstring against the All Blacks and missed the final November Series win over Australia and the whole of Leinster's December programme as he looked to get to the bottom of the issue.
He returned to action against Zebre two weeks ago for 49 minutes and got through 56 minutes in last week's win over Montpellier.
Last night, however, he was forced off mid-way through the first half, meaning he has amassed just 127 minutes since the defeat to New Zealand on November 19. Leinster needed Dan Leavy's try, converted by Sexton's replacement Ross Byrne, and a big late defensive effort, to get them the two points they required.
The number crunchers will tell you that Ulster's clash with Bordeaux-Begles today is more than just a dead-rubber but, in reality, unfavourable results in the last round for each side all but ended their interest in the competition.